Bus bar bushing structure for electrical apparatus casings



Sept. 16, 1952 Filed April 26, 1949 w. G. J BUS BAR BUSHING AMES STRUCTURE FOR ELECTRICAL APPARATUS CASINGS 3 Shoots-Sheet 1 INVENTOR William G. James.

ATTORNEY Sept. 16, 1952 w. a JAMES 2,611,002

BUS BAR mamas mucrm: ma ELECTRICAL APPARATUS CASINGS Filed April 26, 1949 3 Sheets-Sheet 2 Fig. 3.

56 3 5| 52 52 35 39 55 33 57 32 53 3| ,5 B 5 l6 5 B 5 '2 H I 4 n n H I2 4 I n i a ,1 I 4 I I H l l I Fig.4. I33 25 WITNESSES: INVENTOR William 6. James. W A Mas ATTORNEY Patented Sept. 16, 1952 BUS BAR BUSHING STRUCTURE FOR ELECTRICAL APPARATUS CASINGS William G. James, West Middlescx, Pa., assignor to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Application April 26, 1949, Serial No. 89,786

4 Claims.

My invention relates to electric induction apparatus such as transformers and particularly to the method and means for tightly sealing the terminal conductors of such apparatus in the location where they pass through the cover or wall of the casing or tank in which such apparatus is enclosed.

In certain transformers, such as furnace transformers, the low-voltage terminal conductors are large in cross sectional area and carry high current at low voltage. Such conductors commonly consist of a number of bus bars spaced apart and checked in arallel circuit relation.

'It is desirable that the space within the transformer tank or casing be tightly sealed from the space outside of the casing so that air and moisture from without will not enter the tank and so that oil and gas under limited pressure will be the apparatus casing.

The invention is particularly adapted for use with low voltage bus bar bushing assemblies such as are used in furnace transformers. Abus bar bushing'assembly for such use should, in addition to the abovestated objects of the invention, have the following characteristics:

It should require a minimum of space have a high resistance to corrosion, not absorb moisture and should be elastic and withstand temperatures ranging'from minus 50 centigrade to plus 75 centigrade without cracking or losing its elasticity.

l The bushing assembly should not be affected by oil or oil fumes toany great extent or by acids or alkalies, it must be capable of bonding well to copper.

The sealed bus bar bushing assembly structure should be of such construction that it can be left'in place without breaking the seal when the cover to the transformer is removed and it must be capable of withstanding an internal pressure of eight pounds within the transformer casing.

vide a low-voltage bus bar bushing assembly having the above-indicated desirable characteristics.

Other objects and advantages of the invention will appear from the following description of certain preferred embodiments thereof, reference being had to the accompanying drawings in which:

Figure 1 is a perspective view of a portion of the cover of a transformer casing provided with a low-voltage bushing assembly structure constructed in accordance with the invention;

Figure 2 is a plan view of the bushing assembly structure shown in Figure 1 with portions broken away;

Figure 3 is a view in vertical section through the structure shown in Figs. 1 and 2;

Figure 4 is a plan view of a portion of a sheet of insulating material used in the bushing assembly structure;

Figure 5 is a view in enlarged vertical section generally similar to Fig. 3 with slight modifications;

Figure 6 is an end view of the bushing assembly shown in Figs. 1 and 2;

Figures 7 and 8 are edge and plan views, respectively, of an intermediate spacer member for use in one embodiment of the bushing assembly of the invention;

Figures 9 and 10 are edge and plan views, respectively, of an end spacer member for use with a plurality of intermediate spacer members having the form shown in Figs. '7 and 8;

Figures 11 and 12 are plan views of an intermediate spacer member and an end spacer member, respectively, for use in one embodiment of the bushing assembly of the invention;

Figures 13 and 14 are plan views of an intermediate spacer member and an end spacer member, respectively, for use in one embodiment of the bushing assembly of the invention; and

Figure 15 is a vertical sectional view similar to Fig. 3 showing another embodiment of the invention. 1

- Referring to the drawings and particularly to Figures l 2, 3 and 6 thereof, a bushing assembly I0 is shown mounted on a cover ll of a transformer casing or tank. The assembly comprises a rectangular steel cover flange l2 welded to the transformer casing cover I l, as best shown at l3 and I4 in Figs. 3 and 5, which cover flange is shown as extending about the rim of a rectangular opening in the cover of the transformer casing through which the low voltage bus bars extend; The cover flange l2 acts as a base or foundation for supporting the entire bushing as sembly structure. 7 An insulating platform is provided for covering the opening in the transformer cover and supporting the entire bushing assembly structure. The platform comprises a supporting structure formed of a plurality of rigid spacer members of insulating material, :such as press board, and "an insulating rubber mat supported on the spacer members. An end spacer member l5, formed of solid insulating material and having the general shape shown in Fig. 12, is provided at each end of the rectangular opening in the easing and is supported on the cover flange 12. A series of intermediate spacer members IE having the general shape shown in Fig. 1l,1are.p1acec1 ber tween the two end spacer members 15 and are also supported at their oppositeends on the cover flange 12 as best shown in Figure 2. The end spacer members If: may be L-shaped as shown in Figure 12 having awidth ii for the greater portion of .its length, and-a width 18 at a widened portion at one end. The dimension it, which is the diiference between the dimensions is and H, corresponds to the thickness of an individual bus bar 2d that extends upwardly between the spacer members of the platform. .The intermediate spacer members is are T shaped. The dimension 2| across the outer end of the spacer member corresponds to the distance between the'centers of the bus bars 2 3, the dimension 22,

indicating the width-of the .narrow end of the spacer member, corresponds to the distance between adjacent faces of bus bars 24,-a-nd the dimension23'corresponds to the width or thickness of the bus bars. spacers are arranged in accordance with a pat- As best shown in Figure 2, the

tern such that the wide ends of the T-shaped spect to the edges of the opening intheicasing cover. The lengths or thespacing members "and lit correspond substantially to the width-of V the rectangular cover opening with a slight overlap in length so that the ends of the spacer members may rest .on and besupported by the cover flange 1-2. -..T-he ibus bars iii are .shownas being formed of two sheets 2,5101" conductingmaterial, such as popper, spacedapart andibraised =tosashorter .barflfi extending through the-bushmg. v

vA gasket Si is provided, extending about the plurality of slabs 10f spacer .membersJ S and J6 between the outerrimof the cover flange J2 and -a steel :spacer ring 32 which a1SO;S1l1fr.0llIldS the 1 spacer members l5 and iii.

A rectangular .mat 3:37 ofjoil and oxygenre- :sistant syntheticelastomer crirubber shegfl, such,

tor example, as polychloroprene -,or silicone rubber, is provided over the plurality of slabs .of

spacer members l5and l6 andvis provided with 1 a plur-ality of rectangular slots .34 positioned to accommodate the palssageofthe bus bars .24 \therthrough. 111e mat 3.3.assistsiin sealing the opening in the casing .cover to prevent the passage f liquid or .gas therethroug'h. 'The mat extends over the entirecasing cover opening and tofthe outer margin of the spacer .ring 3.2 between the spacer (ring 32 ,anda clampr-ing 3i). .A seriesrof studxnembers 3E- bestshown in.Figs.11,.2 3 and ,are provided for passing'through suitable openings in the clamp ring 35, the rubber mat 33, the spacer ring 32, the gasket 3! and are screwthreaded within bores 31 in the cover flange l2 as best shown in Figure 5. Nuts 38 and washers 39 are provided and are screw-threadedly attached to the stud members 38 and for applying pressure to the 'clamp ring 35 to force it toward the coverfiange'fl so as-to-bring pressure between these two members to press the rim of the mat -33 tightly between the cover ring 35 and the spacing ring 32 and to pres the gasket 3! tightly between the :spacer ring 32 and the cover flange i2 to provide a tight seal between the bushing structure vassembly and the apparatus casing to prevent the passage of liquid or gas therebetween.

The edges of the spacer members that rest on the icoveriflange J2 may be cut back to provide a shoulder fill shown in Fig. 5 or shoulder 63 as shown in Figs. '7, 8, 9 and 10 to provide a space for accommodating the head 42 of a bolt 43 and washer M for attaching the spacermembers directly to the cover fiange lz. I

A plurality of rubber bushing sleeves .51 are provided, one for each of the :bus bar terminal leads and areshown as tapering from a greater width at the bottom to a lesser width-at the :top. The bushing sleeves 5| may be formed ofanoil and oxygen resistant syntheticelastomer or rubber such, for-example, as polychloroprene, butadiene-styrene, butadiene-acrylonitrile,-or silicone elastomers and are cemented to the bus bar lead surfac 52 to securea strongand blasting bond between the sleeve 5| and the abar 25. ".The bushing :sleeves 51 are also cemented to the unat .33 along the surfaces 53 to provide a strong bond between 1 them.

,Aiter-therbus .bartermi-nal-leads 24, the bushing sleeves 51 and the .mat :33 have been assembled as above-described, a rubber tape of uncuredsynthetic rubber is appliedias shownat 55 inFi 3 and .Fig. 5 and is wound about the bushing isleve 5| forming .a cover :for-t-hebush-ing sleeve-which extends over the adiacentj arts of the structure including the bus barras sh own rat iifi and the mat 33'asshown at :51. ZI'hisuncuEed iubbentape .when applied is-an unvu-lcanizecl :vlllcanizable rubber with accelerators and sulphur ,or V-a sulphur compound therein-forcausing=it'to vulcanize at room temperature beyond the tacky stage in twenty-fourv hours aiter being applied @and exposed to the airrand to complete'its cure without heat'application iorrming a sealed closure bonded with the bus .bar .25, bu hing {sleeve 51, and themat as. g f- .Irrsomecases, the sleeve 5;! -,may.;be;omi.ttfid and the uncured synthetic rubber vapplied directly :to the-surface -of the bus barZAand the mat-33 ,forming a bond with these members.

In the embodiments of the invention illustrated :in Figs. 1, 2, 3,14 and e, thepluralit y-ofslabs of -spacermemberscomprising thesupporting structure of :the platform correspond to the spafier members l5 and I6 shown in Figs. 12 and 1-1, respectively. The -L-shaped spacer members l5 of Figure 12 are used at the .two .ends ofsthe group -of :spa-cer members and the intermediate jr-shaped members [5 .are used intermediate .to hetwo end members and are arranged'in-accordance with the patternshown in ,Figure 2.

Figures 7 and Bare an edge ,vi and al i de .view, respectively,- of -an intermediate s pacer memberbi and Figs. 9 and 10 are .anjedgeyiew .anda side View, respectivehzof vanend.spams;

member 52. The spacers 62 and 6! maylbensed in p a e of the spacers le -and 15, r spectively;

which have been previously described. The spacer members 6| and 62 have cut away portions along their outer edges to provide shoulders 63 through which holes 64 are provided for accommodating..- I the heads 42 of bolts 43 as shownin Figure 5;

' Figs. 13 and 14 are plan views of another modified form of end spacers 65 and intermediate spacers 66 that may be used in place of the spacers l5 and I6 shown in Figs. 12 and 11, respectively. The spacers 65 and 66 are provided with holes 61 for receiving the shafts of bolts or screws for attaching them to the cover flange l2. Enlarged recesses 68 are provided for receiving the heads of the bolts or screws, thus providing spaces for countersinking them.

Fig. is a vertical sectional view generally similar to Fig. 3, illustrating a bus bar bushing. structure that differs from that shown in Fig. 3'

1; In a bus bar bushing structure for a plurality of terminal conductor leads extending between the inside and the outside of an electrical apparatus casing having an opening therein, an

insulating platform closing the opening in the casing and provided with a plurality of spaced apart openings therein for accommodating the plurality of terminal conductor leads extending therethrough, said platform comprising a plurality of slabs of spacer members of insulating material forming the supporting structure of the platform, the slabs of spacer members extending I across the opening in the casing and adjacent the terminal conductor leads to position them in their desired position within the opening in the casing, said platform including an insulating rubber mat extending along the outside of the plurality of slabs of spacer members and provided with a plurality of spaced-apart openings therein for accommodating the plurality of terminal conductor leads, gasket means between the outer edge of the platform and the casing" adjacent the edge of the casing opening to Prevent the passage of liquid or gas therebetween, and means for tightly sealing the terminal con-,l ductor leads in the openings in the insulating" platform to prevent the passage of liquid or gas between the leads and the platform, said sealing means comprising an oil and oxygen resistant synthetic rubber bushing sleeve about each of the leads extending through the platform, said sleeve being cemented to the lead and to the platform about the lead, and a synthetic rubber tape forming a band positioned over the bushing sleeve and over a portion of the lead extendingfrom the other end of the bushing sleeve.

' 2. In a bus bar bushing'structure for a plurality of rectangular shaped bus bar terminal conductor leads extending between the inside and the outside of an electrical apparatus casing having a rectangular opening therein, a rectangular insulating platform closing the opening in "the casing and provided with a plurality of spaced apart rectangular openings therein for accommodating the plurality of terminal conductor leads extendingtherethrough, said'platform comprising a plurality of slabs ofspacer members of insulating material forming the supporting structure of the platform, the slabs of spacer members extending across the opening in the casing and adjacent the terminal conductor leads to position thern'in their desired position within the opening in the casing, said platform including an insulating rubber mat extending along the outside of the plurality of slabs of spacer members and provided with a plurality of spaced-apart openings'there'in for accommodating the plurality of terminal conductor leads, gasket means between-the outer edge of the platform and the casing adjacent thev edge of the casing opening to prevent the passage of liquid or gas therebetween, and means for tightly sealing the terminal conductor leads in the openings in the insulating platform to-prevent the passage or liquid or gas between the leads and the platform, said sealing means comprising an oil and oxygen resistant synthetic rubber bushing sleeve about each of theleads extending through the platform, said sleeve being cemented to the lead and to the platform about the lead, and a synthetic rubber tape'forming a band positioned over the bushing sleeve and over a portion of the platform abouton'e end of the bushing sleeve and over aportion of the lead extending from'the other end of the bushing sleeve.

3. In a bus bar bushing structure for a plurality of terminal conductor leads extending between the inside and the outside 01' an electrical apparatus casing having an opening therein, an insulating platform closing the opening in the casing and provided with a plurality of spaced apart openings therein for accommodating the plurality of terminal conductor leads extending therethrough, said platform comprising a plurality of slabs of spacer members of insulating material forming the supporting structure of the platform, the slabs of spacer members extending across the opening in the casing and adjacent the terminal conductor leads to position them in their desired position within the opening in the casing, said platform including an insulating rubber mat extending along the outside of the plurality of slabs of spacer members and provided with a plurality of spaced apart openings therein for accommodating the plurality of terminal conductor leads, means for tightly sealing the terminal conductor leads in the openings in the insulating platform to prevent the passage of liquid or gas between the leads and the platform, said sealing means comprising an oil and oxygen resistant synthetic rubber bushing sleeve about each of the leads extending through the platform, said sleeve being cemented to the lead and to the platform about the lead, and a synthetic rubber tape forming a band positioned over the bushing sleeve and over a portion of the platform about one end of the bushing sleeve and over a portion of the lead extending from the other end of the bushing sleeve.

4. In a bus bar bushing structure for a plurality of rectangular bar terminal conductor leads extending between the inside and the outside of an electrical apparatus casing having a rectangular opening in the cover thereof, a cover flange on the casing cover outlining the rim of the opening and forming a supporting base for the bushing structure, an insulating platform ringysurrounding the plurality of slabs, of spacer members and supported :on the cover flange, va sgas ket zbetween the :spacer ring and the cover flan e, the edge of therubber'matextending over the/spacer ring, and means :for tightly sealing the platform to the casing -cover to form a. tight .giointthereb'etween comprising axclamp ring "positioned 'above, the spacer ring-sand :edge of the iubber mat and :meanssfor connecting the nlanip ring; to theeover :flangeand applying pressurefibetweenthe:spacerring and-cover flange ronopposite'sides of the gasket and between the elamp ring and the spacer .ring on vthe opposite :sides of 'the-irim rubberimat, :and means for tightly zsjeal-ing :the terminal conductor leads in openings, :inmthe insulating platform to prewentthe passage of liquid or gas vbetween the leadsand theplatform, said sealingimeans ,oomprising an .oil and. oxygen resistant synthetic rubber bushing sleeve about each of the --l'eads extending through th'e,platform, said sleeve being cemented to thelead. and to the platform about the lead, and -a "synthetic rubber tape forming a band positioned over the bushing sleeveand over aportion of-the; platform about one end of .thebushing sleeve and overa portion ofthe lead extending iromthe other end of the bushing sleeve. e

, WILLIAM G. JAMES.

REFERENCES CITED The following references are ofr'ecordin the file of this patent: a I

UNITED STATES PATENTS v 7 v v .Dat, 

